A disk array device accommodating a hard disk accommodates a removable circuit board unit mounted with the hard disk and circuit components such as a controller. The apparatus that accommodates the circuit board unit in a casing or a rack needs to prevent leakage of electronmagnetic waves from the front surface of the rack accommodating the circuit board unit. Therefore, the circuit board unit accommodated in the rack is electrically connected to the rack and is grounded. In recent years, the number of clock circuits on a circuit board has increased, and the need for strengthening the shielding against electromagnetic waves is increasing.
For this purpose, it is proposed that a metal sheet spring is provided on the upper surface of the circuit board unit, wherein the circuit board unit is pressed against the rack and is electrically connected to the rack (see Japanese Patent Application Unexamined Publication No. 5-243773). However, the sheet spring has a small contact area with the rack, and cannot obtain sufficient electric contact with the rack to shield the circuit board unit. Further, the sheet spring is plastically deformed during long use, resulting in the occurrence of contact failure.
Further, a conventional apparatus has a mechanism of locking the rack after accommodating the circuit board unit in the rack, on the front surface of the unit. This mechanism is necessary to securely connect the circuit board unit with a backboard within the rack. However, recently as the number of circuit connecting ports has increased, it has become necessary to secure a connector-fitting space on the surface of the circuit board unit. Because of the presence of the locking mechanism on the front surface of the circuit board unit, it has been difficult to sufficiently secure the connector-fitting space.